Articulated two-part prosthesis replacing the ankle joint

ABSTRACT

A two-part ankle prosthesis comprises components which are implanted, respectively, in the prepared distal end surface of the tibia and the proximal end surface of the talus and which cooperate to provide a substitute articulated ankle joint. The tibial component has a sagittal fin which permits fixation insertion from anterior to posterior into the distal tibial epiphysis and is serrated or grooved at its sides for better fixation and increase of the weight bearing surface area, and has a concave lower surface matching the convex upper surface of the talar component prosthesis, thus increasing the weight bearing surface and improving the distribution of weight bearing. The flat under surface of the talar component is supported on the prepared upper surface of the talus, the original dome of which has been osteotomized or removed. With the two prostheses in correct positions the tibio-talar joint is converted into a ball and socket type of joint. In a preferred form the tibial component is made of 316 LVM stainless steel and the talar component is fabricated from ultra-high molecular weight polyethylene or other suitable implant material.

ARTICULATED TWO-PART PROSTHESIS REPLACING THE ANKLE JOINT Richard C.Smith, San Pedro, Calif.

Wright Manufacturing Company, Arlington, Tenn.

Aug. 28, 1974 75 Inventor:

[73] Assignee:

[22] Filed:

[2'1] Appl. No.: 501,296

Primary Examiner-Ronald L. Frinks Attorney, A gent, or Firm ScrivenerParker Scrivener and Clarke 1 June 17, 1975 57 ABSTRACT A two-part ankleprosthesis comprises components which are implanted, respectively, inthe prepared distal end surface of the tibia and the proximal endsurface of the talus and which cooperate to provide a substitutearticulated ankle joint; The tibial component has a sagittal fin whichvpermits fixation insertion from anterior to posterior into the distaltibial epiphysis and is serrated or grooved at its sides for betterfixation and increase of the weight bearing surface area,

and has a concave lower surface matching the convex upper surface of thetalar component prosthesis, thus increasing the weight bearing surfaceand improving the distribution of weight bearing. The flat under surfaceof the talar component is supported on the prepared upper surface of thetalus, the original dome of which has been osteotomized or removed. Withthe two prostheses in correct positions the tibio-talar joint isconverted into a ball and socket type of joint. In a preferred form thetibial component is made of 316 LVM stainless steel and the talarcomponent is fabricated from ultra-high molecular weight polyethylene orother suitable implant material.

3 Claims, 5 Drawing Figures PATENTEDJUN 1 1 m5 1 3,889,300

FIBULA MEDIAL MALLEOLUS I "n LATERAL lh B MALLEOLUS NAVICULAR BACKGROUNDOF THE INVENTION The normal human ankle is a joint which is constructedto permit movement in flexion and extension, with some abduction,adduction and rotation capability. Plantar flexion and dorsiflexion arethe major movements of the ankle and may be performed through an angularmovement of approximately 20 dorsiflexion to 50 plantar flexion.Rotation is the relative movement of the tibia and talus about theirsubstantially common vertical axis, the normal rotation limit beingapproximately to either side, an arc of approximately I Diseaseindications of the ankle joint include severe rheumatoid arthritis,osteoarthritis, traumatic arthritis and painful failed arthrodesis. Thediseased ankle joint has heretofore been treated by various local repairprocedures or, in advanced cases, by fusion. The desirability ofreplacement of the ankle joint has been apparent, and momentum towardthis end has been accelerated by the successful invention anddevelopment of implants and procedures for provision of total hip andtotal knee prostheses. However, until the present invention no suchprostheses or procedures were known or available for providing areplacement for the complete ankle joint.

SUMMARY OF THE INVENTION In accordance with the invention an articulatedtwopart prosthesis is substituted for the diseased tibio-talar joint,the structure and implantation of which permits retention of the primaryankle ligaments, and after implantation permits flexion, rotation andsliding movements substantially reproducing the movements of the normalhuman ankle. The components of the prosthesis are a distal tibialimplant having a concave partspherical surface facing the talus, and aproximal talar implant having a dome-shaped convex part-sphericalsurface engaging and co-operating with the concave surface of the tibialcomponent. The tibial component is implanted into a recess formed in thedistal end of the tibia, and the talar component rests on the preparedupper plateaued surface of the talus, both components being formed withmeans to cause their permanent, immobile attachment to their respectivebones with the use of a suitable cement. This two-part prosthesispermits reproduction of the dorsi-flexion and plantarflexion movements,as well as some of the inversion, eversion and rotational movementcomponents of the joint, all at the level of the tibio-talar joint ofthe normal human ankle.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the bonesforming, and adjacent to, the human ankle joint, showing the twopartprosthesis provided by the invention in place, in substitution for thehuman ankle;

FIG. 2 is a side elevational view of the two parts of the ankle and theprosthesis shown in FIG. 1, with the ankle parts at neutral;

FIG. 3 is a front view of the two components of the prosthesis, thetibial component being shown in section;

FIG. 4 is a side elevational view of the two components of theprosthesis, and

FIG. 5 is a bottom view of the talar prosthesis.

DESCRIPTION OF THE INVENTION In FIGS. 1 and 2 of the drawings theprincipal parts of the human leg and foot adjacent and forming the ankleare shown and labeled, and as these are well known to those skilled inthe medical and other arts to which this invention relates they will notbe further described here. This figure also shows the two components ofthe prosthesis provided by this invention, in operative association withthe illustrated parts of the body. These components are a tibialcomponent which is constructed and intended to be attached distally tothe tibia, and a talar component which is constructed and intended to beattached proximally to the talus.

The distal tibial component is designated generally by the letter A, isformed of metal such as stainless steel, and comprises a lower or basepart 2 which is preferably circular in shape and disposed substantiallyhorizontally when implanted, and an upper part 4 which extends upwardlyfrom the base part and is constructed and adapted to be driven into thedistal tibial shaft from anterior to posterior, as shown in FIG. 1 inorder to attach the component to the tibia.

The base part 2 of the tibial component has a lower surface 6 thecentral part of which is formed as a concave, downwardly-facing surface8 of part-spherical shape. This surface, which engages thesimilarly-shaped upper surface of the talar component, is polished to amirror finish, while the other parts of the component may have a dullfinish. The upper part 4 of this component is a saggital fin havingupwardly extending side walls 10, 12 which are spaced laterally of theanteriorposterior axis of the ankle joint and which at their upper endsjoin a flat upper surface 14. The lower parts of the side walls arecurved to join the base part 2, as shown at 16, 18, and the upper partsare parallel. Upwardly and outwardly extending saw-toothed ridges andgrooves 20 are formed in the upper parts of the side walls of the finand extend in the anterior-posterior direction. The fin has a notch 22at the distal posterior part of its base, adjacent the upper surface ofthe base part 2 of the implant, which co-operates with the osteotomyslot prepared in the distal posterior area of the tibia during theimplantation procedure for the purpose of locking the component in placein the osteotomized area of the tibia.

Surrounding the central, concave, downwardly facing surface 8 is anannular surface 24 the outer and inner peripheral edges of which areconvexly rounded to provide smooth contact with the talar prosthesis,which is most important in the event of an unavoidable rocking motionoccurring between the two components which would otherwise result ingouging or digging in of the plastic talar component by the metal tibalcomponent.

The talar component of the prosthesis is designated generally by theletter B, is formed of a synthetic plastic material, is preferablycircular in shape and substantially horizontal when implanted, and whichmay be somewhat larger in diameter than the circular base 2 of thetibial component as shown in FIG. 3. This base part 30 has a generallyflat lower surface which engages and rests on the upper plateau surfaceC of the talus after suitable preparation thereof. The upper surface ofthe component rises above thebase 30 to provide an upwardly convex dome32 which is part-spherical in shape and has the same radius of curvatureas the downwardly facing concave lower surface 8 of the tibial componentso that the two surfaces will exactly mate.

Means are provided on the lower surface of the base part 30 of the talarcomponent for securely and permanently connecting the component to theprepared plateau surface of the talus, and in its preferred form, whichis shown in FIG. 5, this means takes the form of two groups 40, 42 ofcurved ridges 44 each of which is shaped as a triangle in cross sectionand has a sharp lower edge, and which by its configuration interlockswith the cement on the talar surface, the ridges of each group beingconcentric and the centers of the two groups being diametricallyopposite each other as shown in FIG. 5. A plurality of holes or recesses46 extend upwardly from the lower surface of the component and into thebody thereof in a direction perpendicular to a tangent of the dome 32,and the cement which is used to connect the component to the talalplateau extends into these holes and provides an additional lockingaction.

The talar component of the prosthesis is preferably made of ultra-highmolecular weight polyethylene or other material suitable for humanimplant purposes. In accordance with known procedure, a wire may bepositioned in a groove formed in an outer surface of one or bothcomponents which serves as an X-ray locator and a reference line topermit wear of the prosthesis to be measured while in use, as X-raystaken at one year or at some other interval will indicate any variationin distance between the bottom edge of the tibial component and thewire.

The two prosthetic components are designed to work together as a unit insuch a fashion as to emulate the normal motions characteristic of ahealthy human ankle. The positions of the bearing surfaces permitflexion of the talus with respect to the tibia with approximately 20dorsiflexion to approximately 40 plantarflexion, thus substantiallyreproducing the range of flexional movement of the human ankle. Thepart-spherical shape of the dome of the talar component permits thebearing surface of the tibial component to ride level on the talar domeduring rotational movements of the ankle without riding up on the sidesof the dome, which would produce binding between the tibia] and talarcomponents. The two components are designed so that in use thetheoretical limits of motion are from 20 dorsi-flexion to 40plantar-flexion, and to 10 of rotation and inversion/eversion. Theprosthesis has great utility in replacing the rheumatoid, theosteoarthritic, the traumatic arthritic, and the post-failed arthrodesisankle. Its use produces many good results, among them being improved andmore efficient gait, conservation of energy (a study reveals a 6 percentabove average energy expediture with one ankle immobilized, nine percentwith two immobilized), less stress and subsequent wear at the knee aboveand at the forefoot below the prosthesis with better weight distributionon the foot during ambulation, especially over rough ground, improvedtransfer capability from the seated to the standing posture, especiallyif the knees are also diseased, ability to wear regular shoes whenequinas capability is retained, with women being able to vary heelheights to I '4 meet fashion demands, and easier post-operative recoveryas the patient merely awaits soft tissue healing, avoiding the,l5 to 20percent reported incidents of failed bony fusion.

1 claim:

l. A two-part prosthetic device for arthoplasty of the human anklejoint, comprising a tibial component for replacing at least a part ofthe prepared distal end of the tibia, and a talar component forreplacing at least a part of the prepared proximate surface of thetalus, the tibial component comprising a base part having a downwardlyfacing concave surface of part-spherical shape and a part extendingupwardly from the base part and having spaced side walls extending in ananteriorposterior direction when implanted and having a notch in itsdistal posterior base to receive an osteotomy slot prepared in thedistal tibia to lock the component in place, the talar componentcomprising a base part having an upwardly facing convex surface which ispartspherical in shape and has the same radius of curvature as that ofthe concave surface of the tibial component and on which the concavesurface rests when the twopart prosthesis is in place, and means on thelower surface of the talar component for engaging into the bone of thetalus to increase the connection of the component thereto.

2. As a new article of manufacture, a tibial prosthesis component forreplacing at least a part of the prepared distal end of the tibia, thetibial component comprising a unitary integrally formed deviceconstructed and adapted to be connected to the distal end of the tibiaand to serve in lieu of the articulating surface thereof, said tibialcomponent comprising a lower base part of circular shape having apolished downwardly facing bearing surface which is spherically concave,and above the base part having an upwardly directed bone fixationelement for implantation in the tibial shaft and having a notch in itsdistal posterior base part to receive an osteotomy slot prepared in thedistal tibia to thereby lock the component in place, and a roundeddownwardly facing edge surface surrounding the bearing surface toprovide smooth transitional contact with a talar prosthesis, whereby thespherical concave bearing surface provides all rotational and slidingcapabilities between a two-part prosthesis when implanted and operative.

3. As a new article of manufacture, a talar prosthesis for cooperatingwith a tibial prosthesis to form an articulated prosthesis replacing theankle, said talar prosthesis comprising a circular body having agenerally flat lower surface for engagement with and connection to aprepared proximate plateau surface of a talus, curved ridges extendingdownwardly from the lower surface of the talar component and havingdownwardly directed sharp lower edges for better connection of the talarprosthesis to the prepared surface of the talus, having a convexpart-spherical upper surface extending upwardly from the periphery ofthe lower surface and forming a bearing surface to accept the downwardlyfacing part spherical concave bearing surface of a tibial prosthesis,and at least one recess formed in the body and opening to the lowersurface thereof to receive cement used in connecting the talarprosthesis to the prepared proximate surface of the talus.

1. A two-part prosthetic device for arthoplasty of the human anklejoint, comprising a tibial component for replacing at least a part ofthe prepared distal end of the tibia, and a tAlar component forreplacing at least a part of the prepared proximate surface of thetalus, the tibial component comprising a base part having a downwardlyfacing concave surface of part-spherical shape and a part extendingupwardly from the base part and having spaced side walls extending in ananterior-posterior direction when implanted and having a notch in itsdistal posterior base to receive an osteotomy slot prepared in thedistal tibia to lock the component in place, the talar componentcomprising a base part having an upwardly facing convex surface which ispartspherical in shape and has the same radius of curvature as that ofthe concave surface of the tibial component and on which the concavesurface rests when the two-part prosthesis is in place, and means on thelower surface of the talar component for engaging into the bone of thetalus to increase the connection of the component thereto.
 2. As a newarticle of manufacture, a tibial prosthesis component for replacing atleast a part of the prepared distal end of the tibia, the tibialcomponent comprising a unitary integrally formed device constructed andadapted to be connected to the distal end of the tibia and to serve inlieu of the articulating surface thereof, said tibial componentcomprising a lower base part of circular shape having a polisheddownwardly facing bearing surface which is spherically concave, andabove the base part having an upwardly directed bone fixation elementfor implantation in the tibial shaft and having a notch in its distalposterior base part to receive an osteotomy slot prepared in the distaltibia to thereby lock the component in place, and a rounded downwardlyfacing edge surface surrounding the bearing surface to provide smoothtransitional contact with a talar prosthesis, whereby the sphericalconcave bearing surface provides all rotational and sliding capabilitiesbetween a two-part prosthesis when implanted and operative.
 3. As a newarticle of manufacture, a talar prosthesis for cooperating with a tibialprosthesis to form an articulated prosthesis replacing the ankle, saidtalar prosthesis comprising a circular body having a generally flatlower surface for engagement with and connection to a prepared proximateplateau surface of a talus, curved ridges extending downwardly from thelower surface of the talar component and having downwardly directedsharp lower edges for better connection of the talar prosthesis to theprepared surface of the talus, having a convex part-spherical uppersurface extending upwardly from the periphery of the lower surface andforming a bearing surface to accept the downwardly facing part sphericalconcave bearing surface of a tibial prosthesis, and at least one recessformed in the body and opening to the lower surface thereof to receivecement used in connecting the talar prosthesis to the prepared proximatesurface of the talus.